Convert STL
to SLDPRT.

Updated 2026-10-19

To convert STL to SLDPRT, drop the .stl into the converter below and download a native .sldprt. Planes, cylinders, cones, spheres and tori in the mesh are usually rebuilt as true surfaces, so a hole is one cylindrical face you can dimension, not a ring of slivers; where none of them fits, the region stays faceted and the download says which you got. 2 solid conversions a day need no account. SOLIDWORKS can import an STL itself, but only as facets: one flat face per triangle.

2 solid-geometry conversions a day with no account. No card, no install.

No account needed
Drop a STL file.stl · up to 200 MB

On our servers. No account: deleted within 24 hours. Signed in: kept until you delete them. Never shared or used for training.

ResultSurfaces recovered

Planes, cylinders, cones and spheres are rebuilt as true surfaces where the triangles fit them, and freeform regions as smooth patches, in a closed solid that mates, measures and cuts like modelled geometry. Where they cannot be rebuilt the body is faceted instead, and every conversion says which of the two you got.

The STEP as a faceted converter writes it: 524 flat faces, one per triangle.

One face per triangle · 524 faces. Each hole is a ring of flat strips you cannot select or measure.

The STEP from MeshWeave: 10 faces, 7 planes and 3 cylinders.

MeshWeave · 10 faces: 7 planes and 3 cylinders. The hole measures Ø12.00 mm.

The same 524-triangle STL, converted both ways and coloured one shade per face. A synthetic test part, run through the converter, not drawn.

Surfaces are only as accurate as the mesh they come from, and there is no feature history.

ChangesSTL → SLDPRT

What changes between STL and SLDPRT

An STL is triangles and nothing else: no surfaces, no edges, no unit, no history. A SLDPRT is a SOLIDWORKS part built from true faces. The work in between is recognising what surfaces the triangles were approximating.

Regions that lie on a plane, cylinder, cone, sphere or torus are fitted, and a fit is kept only when every vertex of the region lies close to it. Kept fits become real faces with real edges between them, so SOLIDWORKS can select a face, measure a radius and mate to a hole. Regions that fit none of those become smooth patches, or stay faceted as a last resort.

Limits worth knowing: accuracy follows the mesh, so export the STL as finely as you can. An STL with gaps may arrive as surface sheets rather than a solid. The numbers are read as millimetres. The part opens as one imported body in SOLIDWORKS 2026, with no feature tree, and nothing can recover the features the mesh was made from.

HowThree steps
  1. Drop your .stl file above — up to 200 MB without an account.
  2. SLDPRT is already selected as the output.
  3. Download the .sldprt. Without an account, files are deleted within 24 hours; signed in, they are kept until you delete them.
FormatsWhat you are holding

STL file (stereolithography) (.stl)

STL is the lingua franca of 3D printing: a flat list of triangles. No unit, colour, material or history — a cylinder is a fan of flat strips. The missing unit is the classic cause of scale accidents. Every slicer and mesh tool reads it.

You are printing, meshing or sending to a bureau — where triangles are what is wanted.

SOLIDWORKS part file (.sldprt)

A SLDPRT file is a single SOLIDWORKS part: the exact solid — true planes, cylinders and splines — plus its feature history, sketches, material and custom properties. It is proprietary, so nothing else on your machine may open it. Assemblies are SLDASM files. One SLDPRT can hold several bodies, and those should stay separate when converting.

You were sent a SLDPRT, do not have SOLIDWORKS, and need the geometry in something your CAD system, slicer or mesher opens.

Questions11 answered
Why not just open the STL in SOLIDWORKS?
You can, but SOLIDWORKS imports it as facets, one flat face per triangle, so nothing round can be selected or dimensioned. Here the round faces come back as round faces.
Will the part have a feature tree?
No. An STL never had one and no tool can recover it. You get one solid body to measure, mate and add features to.
What unit should the STL be in?
Millimetres. STL records no unit, so a part modelled in inches should be scaled before converting.
Which SOLIDWORKS release opens the part?
SOLIDWORKS 2026. For 2025 or 2024, re-save it with the older-version converter, or convert the STL to STEP, which every release imports.
Is the STL to SLDPRT converter free?
Yes. 2 solid-geometry conversions a day with no account, of 5 in total. A free account converts 4 solid files a day and adds 25 credits. No card.
Does the SLDPRT result have real curves, or flat facets?
The mesh comes back as a SLDPRT solid with real surfaces: a round hole becomes one cylindrical face. Planes, cylinders, cones and spheres are rebuilt as true surfaces where the triangles fit them, and freeform regions as smooth patches, in a closed solid that mates, measures and cuts like modelled geometry. Where they cannot be rebuilt the body is faceted instead, and every conversion says which of the two you got. Surfaces are only as accurate as the mesh they come from, and there is no feature history.
Will the SLDPRT file open in Fusion 360, Inventor or Onshape?
Yes. SLDPRT is read directly by Fusion 360, Inventor, Onshape, SOLIDWORKS, Creo, NX and FreeCAD. It usually arrives as a solid body with true surfaces, without feature history, and the conversion says when it came back faceted instead.
Can you turn the triangles back into proper CAD surfaces?
Usually. Where the triangles fit them, planes, cylinders, cones and spheres come back as true surfaces, so a hole is one cylindrical face with a radius you can measure, and freeform regions become smooth patches. Where nothing fits, the region stays faceted, and the conversion says which you got. Accuracy follows the mesh, so start from the finest STL you have.
How big a file can I convert?
To a mesh format like STL: 300 MB with a free account, 200 MB without one. To STEP, Parasolid or SLDPRT: 140 MB, because rebuilding a solid takes about twice the memory of writing a mesh. Maker and Studio convert up to 830 MB and 380 MB — a large conversion on a paid plan gets the server to itself.
Is it safe to upload my STL file?
Files travel encrypted and are processed by machine on our own servers — no third parties, no ads or trackers, no AI training.
Is my STL file deleted after converting?
Without an account, the upload and the result are deleted within 24 hours. With an account, both stay in your files until you delete them; deleted files leave our servers within 24 hours.
Beyond convertingSame file, four workspaces

Keep the part open: fill it with a lattice, check it with FEA, texture a surface, or slice it into cut-ready sheets. These workspaces are in early access — create an account, then apply from inside the app.

Create free account See pricing

ReadWhy this works the way it does
AlsoOther ways in
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Going the other way? Convert SLDPRT to STL.

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